/*
 * Copyright 2006 Sascha Weinreuter
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.intellij.lang.regexp.psi;

import org.jetbrains.annotations.Nullable;

public interface RegExpBackref extends RegExpAtom {
    /**
     * Returns the group-index the backref refers to
     * Could be negative for relative references: {@link org.intellij.lang.regexp.RegExpCapability#PCRE_BACK_REFERENCES}
     * @return the index of the group this backref refers to
     */
    int getIndex();

    /**
     * @return The referenced group, or null if no such group exists
     */
    @Nullable
    RegExpGroup resolve();
}
